Radar false alert reduction

ABSTRACT

A radar detector suppresses alerts from vehicle guidance systems, by sweeping for a consistent radar signal; the center frequency of the signal is stored and the detector suppresses warnings of radar signals near that frequency. The detector uses an enhanced method for suppression of signals near a known location of a false signal source; in the event the detector detects a radar signal and finds a matching stored false signal, the detector will first compare the strength of the received signal to a threshold strength that is computed based upon the distance of the detector from the stored false signal, and will only suppress signals below threshold. The detector includes a camera directed to the road in the vicinity of the vehicle. Image data from the camera is processed to identify police vehicles as identified by flashing lights, a profile including a rooftop light bar and/or highly contrasting colored panels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of currently pending U.S. applicationSer. No. 13/794,867 filed Mar. 12, 2013, which is incorporated byreference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 6,670,905, invented by the inventor named herein, andhereby incorporated by reference, discloses a GPS enabled radar detectorthat uses GPS to aid in the management of non-police-related orotherwise irrelevant sources of radar signals, permitting the detectorto dynamically improve its handling of such sources and reduce falsealerts. The detector references previously-storedgeographically-referenced information on such sources, and compares thedetector's current location to locations of known stationary false alertsources of radar to improve the handling of detection of those sources.When the detector is within a threshold distance of a stored false alertsource, the detector suppresses alerts to frequency bands or sub-bandsthat correlate to the frequency of the known false alert source. Falsesources may be manually identified and “locked out” by the user, or maybe automatically identified based upon multiple repeated encounters ofthe detector with the source at a particular geographic area.

Systems embodying the invention of the '905 patent have beensuccessfully commercialized by the assignee of this application, andhave proven commercially viable, but those systems remain subject tocertain vulnerabilities which will be discussed herein.

One vulnerability is false radar alerts created by traffic sensingequipment installed in many major metropolitan areas. The signals fromtraffic sensors appear in police radar bands, and are emitted in shortbursts at a regular cadence. Because traffic sensors are geographicallyfixed and operate in a consistent frequency range, it is possible for aradar detector user to manually lockout traffic sensor alerts; however,traffic sensor signals do not appear regularly enough to be reliablylocked out automatically, at least without a greater than normal numberof encounters. In response to this source of false signals, the assigneedeveloped a Traffic Sensor Rejection (TSR) method, which searches forthe characteristic cadence and frequency of traffic sensor systems, andsuppresses alerts of those systems using a processing logic separatefrom the location-based lockout described in the '905 patent. Becausethis logic is separate from location based lockouts, police radar orpolice-like false signal sources appearing in the same frequency bandand same geographic area as a TSR signal will not be suppressed by theTSR method, which is preferable to a location based frequency lockout inthat area which would potentially suppress police signals as well.

Another vulnerability is the increasing number of vehicle-borne radarsources. Examples include radar based systems attached to vehicles forlane sensing, adaptive cruise control, collision prevention, automatedparking, and the like, which will be collectively identified herein as“vehicle guidance systems”. One specific example of these systems is theMercedes-Daimler Distronic system, which emits a 24.125 GHz K-bandfrequency to provide adaptive vehicle cruise control, which is in theband used by police and normally detected by a radar detector wheneverit is near to an operative Distronic system. Vehicle guidance systemsoften create an annoying false alarm when a radar detector passes thesource vehicle, and this false alarm cannot be suppressed based onlocation because the signal source is a mobile vehicle. The annoyancebecomes critical when the vehicle with the radar detector is itselfcarrying a vehicle guidance system; the constant alerting in thisscenario essentially puts the vehicle operator to a choice betweendisabling an entire band of radar detection (or foregoing radardetection entirely), and disabling the vehicle guidance system.

Efforts are underway by the assignee to identify characteristic cadencesor other profiles of vehicle guidance systems, much as was done for TSR,and some have been effectively identified and suppressed via a separatemethodology like that used for TSR. However, some vehicle guidancesystems have so far eluded effective characterization in this manner.

A third vulnerability of the existing systems is that location basedlockouts can potentially prevent alerting to police radar that happensto appear in the same frequency range and within a geographic range of astationary source. As radar detectors become more sensitive theeffective scope of a location lockout area must increase to ensure thatalerts to the false signal are suppressed, which entails also increasingthe geographic area in which alerts will be given to other sources inthe same frequency ranges, including police radar sources. A regularcriticism of location based lockout methods is the potential a radardetector will fail to alert to police radar which happens to coincide inlocation and frequency to a stored false signal. It would be desirableto improve the manner in which stationary false signals are processed toreduce the likelihood that an alert to actual police radar issuppressed.

A final vulnerability of the existing systems is the continuing adoptionof ‘instant-on’ and line of site speed monitoring technology. A radardetector provides advance warning of police speed monitoring bydetecting the monitoring of other cars that are typically ahead of thevehicle carrying the radar detector. Modern radar guns which operate inthe Ka band can turn on and off rapidly, on a car-by-car basis. If thereis a long enough interval between uses of the gun, a radar detector willnot be able to pick up the stray radar emissions from previousinterrogations to give advance warning of the use of radar. Laser(LIDAR) speed detection poses an even greater challenge for the reasonthat it is generally line of sight and provides very little advancewarning of its use, if any. To respond to these challenges the assigneeand others have developed social networks through which drivers canshare radar events and sightings of police into a social network, sothat a warning can be delivered to other drivers approaching the area.Unfortunately, users of social networks often report police activitiesthat are not actually speed traps, for example, social network users maywarn of a police car that is driving with traffic, waiting at a trafficlight on a cross street, or involved in other activities that are notcharacteristic of a fixed location speed trap. Alerts that can beconfirmed, e.g., via radar detection, are more reliable, but the socialnetwork cannot rely only upon radar-based alerts, for the reason that apolice car on station at a speed trap may be using instant-on radar orLIDAR, in which case not every vehicle will be exposed to radar.Accordingly, it would be useful to provide a method for betteridentifying particular situations which are actually indicative of aspeed trap, such as police positioned at a roadside monitoring passingtraffic, or operating its light bar adjacent to a stopped car.

SUMMARY OF THE INVENTION

The present invention addresses the shortcomings of the prior art byimproving a radar detector in accordance with several different aspects.

According to a first aspect of the present invention, the challenge offalse alarms from vehicle guidance systems is addressed by introducing alocal source lockout sequence into the operation of a radar detector.The local source lockout sequence may be performed at any time ofdetector operation, but in one example it is performed when the radardetector is first powered. In the local source lockout sequence theradar detector sweeps for radar signals that are steadily present and/orappear to be location independent, and thus are characteristic ofvehicle guidance systems on the vehicle carrying the radar detector. Ifsuch a signal is found, the radar detector identifies a center frequencyfor the signal, and stores that center frequency for future reference.Thereafter, the detector will suppress warnings of a radar signal thatis detected at frequencies that are near to the stored center frequency.The center frequency may be in any of the sensitive bands of the radardetector, including the K-band, Ka-band or X-band. Furthermore, thedetector may have a setting to enable or disable the local sourcelockout sequence, so that this sequence may be disabled, e.g., forvehicles that do not have vehicle guidance systems. Furthermore, thedetector may identify cases in which two discriminable signals appearwithin the range of the stored center frequency, and in those cases, thedetector will produce an alert (provided there is no applicablelocation-based lockout), thus avoiding to the extent possiblesuppressing police radar alerts.

In a second aspect, the invention features an enhanced method forsuppression of signals near a known location of a false signal source.Specifically, in the event the detector detects a radar signal and findsa matching stored false signal (that is, the detected signal is withinthe frequency subrange of the stored false signal, and the detector isin a location near to the stored a known false signal source), ratherthan suppressing the received signal, the detector will first comparethe strength of the received signal to a threshold strength that iscomputed based upon the distance of the detector from the stored falsesignal, and if the received signal exceeds the threshold strength thealert of the received signal is reported to a more prominent extent thanif the received signal is below the threshold strength. For example,signals below the threshold may be reported by a minimal visual alertwithout accompanying warning sounds, whereas signals above the thresholdmay be reported with visual and audible cues in the manner of otherradar signal detections. In the specific embodiment disclosed, thethreshold is set at 3 dB higher than an expected signal strength, andthe expected signal strength is computed according to an inversesquare-law relationship between signal strength and the distance of theradar detector from location stored for the false signal source. In amost particular embodiment, signals falling below the threshold aretracked over time and in the event they are persistent over time, analert is generated to those signals notwithstanding signal strengthbelow the threshold.

According to a third aspect, the invention features an enhanced methodfor identifying police activity that is indicative of a speed trap, toimprove the reliability of warnings of police activity delivered viasocial networks. To implement this method, a camera is integrated into aradar detector, the camera directed to the road in the vicinity of thevehicle. The radar detector gathers image data from the camera andprocesses that data to identify police vehicles in the image. Inparticular embodiments the processing by the radar detector evaluatessequential images to identify flashing lights characteristic of afunctioning light bar on a police or emergency vehicle. In anotherembodiment the processing by the radar detector evaluates one or moreimages to identify the profile of a vehicle that is characteristic of apolice vehicle (e.g., having a rooftop light bar and/or highlycontrasting colored panels) and/or which is stationed to monitortraffic, such as at a roadside in a position that is not correlated withcrossing traffic at an intersection. The radar detector may respond toimage(s) indicative of police activity by automatically generating analert to other drivers in a social network, or by suggesting to avehicle operator the generation of such an alert, subject to validationby the vehicle operator.

The above and other objects and advantages of the present inventionshall be made apparent from the accompanying drawings and thedescription thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a radar detector block diagram according to principles ofthe present invention;

FIG. 2 shows a flow chart of operation of the radar detector of FIG. 1performing a lockout of vehicle guidance related false signals;

FIG. 3 shows a flow chart of operation of the radar detector of FIG. 1performing evaluation of a detected radar signal in connection withstored locations of false signals;

FIG. 4 shows a flow chart of operation of the radar detector of FIG. 1performing evaluation of image or video data from the camera included inthe detector.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description of the embodiments given below, serve toexplain the principles of the invention.

FIG. 1 illustrates a radar detector 20 according to principles of thepresent invention, which features a fusion processor 22 for controllingall functions of the unit. Fusion processor receives information onradar signals from a conventional microwave receiver 24, coupled toprocessor 22 via a digital signal processor (DSP) 26. Microwave receiver24 and DSP 26 may utilize any of the techniques known in the art fordetection of radar signals, for rejecting noise and increasingdiscrimination between actual and spurious police radar signals.Further, receiver 24 and DSP 26 may be controlled by an optional secondCPU 25, which can enable additional signal evaluation beyond that whichis possible using a DSP.

Processor 22 is further connected to a laser detector 28 for detectingpolice LIDAR signals. Processor 22 is further connected to a GPSreceiver 32 and a separate differential GPS (DGPS) receiver 30, suchthat differential GPS methodologies may be used where beacon signals areavailable.

Processor 22 executes a stored program, found in integrated or off-chipelectrically erasable programmable read only memory (EEPROM), flashmemory, or masked read only memory (ROM). The processor is programmed tomanage and report detected signals in various ways depending on itsstored program, including by methods described herein.

Processor is coupled to a cellular interface 34 to permit social networkinteraction with servers and data from other radar detectors. In oneembodiment cellular interface 34 comprises a BLUETOOTH® (IEEE 802.15.1)or other 802.1x compliant radio for connecting to a cellular phone,smart phone, or other cellular device, which may operate on the controlof a separate application such as the assignee's “Escort Live”smartphone app. In another embodiment cellular interface 34 may itselfcomprise a cellular radio for direct connection to cell towers. Othercommunication technologies may also be used for social networkinteraction, such as satellite telephony, mesh networking via wifi,BLUETOOTH® (IEEE 802.15.1), or 802.1x radio of other kinds, or otherstandards.

The radar detector further incorporates a user input keypad or switches36. Operational commands are conveyed by the user to processor 22 viathe keypad. Processor 22 is further connected to a display 38, which maycomprise one or more light emitting diodes for indicating various statusconditions, or in a more feature-rich device, may include analphanumeric or graphical display for providing detailed information toa user. A speaker 40 is also provided to enable processor 22 to deliveraudible feedback to a user under various alert conditions, as iselaborated below.

Processor 22 may further include a camera 42, positioned on afront-facing, side facing or rear facing surface of the device, and avideo processor 44, such as for processing video or still images fromcamera 42 according to methods that are described herein.

Processor 22 is further coupled to a Universal Serial Bus (USB)interface 46 that provides a means for uploading and downloadinginformation to and from processor 22. USB interface 46 may be used toautomate the assimilation of coordinate information into data structuresin EEPROM 34. USB interface 46 may also be used to interface thedetector to a separate host computer or product application containing alarger storage capacity than available from internal memory. USBinterface 46 may also be used for the purposes of firmware upgrade. Fromtime to time updates and bug fixes may become available, e.g. through amanufacturer website. USB interface 46 will enable the user to apply theappropriate firmware upgrade or bug fix. USB interface 46 could also beused to add other user waypoints.

Referring now to FIG. 2, methods for suppressing false alarms caused byvehicle guidance systems can be described. In general, the method ofFIG. 2 uses a frequency based “lockout” (not location based), which canbe used on all radar detector devices (GPS, or non-GPS based detectors).The feature can be enabled or disabled in the device Preferences. On GPSbased detectors, consistency of an apparent false signal the vehiclespeed can be used as a factor to disable a locked frequency range atspeed ranges where the vehicle guidance systems are not enabled.

The lockout sequence 204 is enabled under several circumstances. Forexample, when the unit is powered on 200, if the vehicle guidancesuppression mode is enabled 203, a lockout sequence 204 is performed.Alternatively, when the user encounters a vehicle guidance interference,and in response enables 202 the vehicle guidance suppression mode via asequence of button presses, the lockout sequence may be performed. Athird alternative is for the vehicle guidance lockout sequence to beautomatically enabled 201 upon detection of a time consistent alert thatis frequency consistent with a vehicle guidance system.

The lockout sequence 204 scans 206 the radar band for a radar signalconsistent with the frequencies of known vehicle guidance systems. Thesignal is then evaluated 208 for consistency over time with the on/offcadence of the known vehicle guidance system. If these tests are passed,then in step 210 the center frequency of the short-range sensor of theguidance system is identified, and stored 212. The detector then padsthat frequency above and below to allow for drift of both the signaland, if appropriate, the radar detector.

After a lockout has been stored, if (step 214) the detector identifiesone signal in the range of the stored center frequency, it suppresses218 an alert to the signal. For example the device may show a smallvisual indication that there is a detected signal, but it has beendetermined to be a vehicle guidance system. As a further optional test(step 216), in a GPS-enabled radar detector, the speed of the vehicle asreported by the GPS receiver may be compared to the known speed rangesof operation of the vehicle guidance system (some systems do not operatebelow a threshold speed, or above a threshold speed). Using thisoptional test 216, the alert is suppressed only if the vehicle's speedis consistent with operation of a vehicle guidance system.

When a lockout has been stored, if (step 220) the detector identifiestwo signals in the range of the stored center frequency, then thedetector will proceed to step 220 and produce a normal alert to theradar signal, if the signal is not subject to filtering on other bases(such as TSR filtering or GPS-location based lockout)

Referring now to FIG. 3, improvements to location-lockout methods can bedescribed. The background principle to this method is that, in freespace, electromagnetic waves obey the inverse-square law, which statesthat the power density of an electromagnetic wave is proportional to theinverse of the square of the distance from a point source. Therefore thesignal level measured by a radar detector will vary in proportion to thedistance between it and a signal source that is detected by the radardetector. Current location based false signal rejection methods preventthe detection of all “qualified” signals detected within a lockoutregion. The lockout region, however, may encompass a large area wherethe radar detector is relatively sensitive.

A significant enhancement will be realized by redefining a lockoutregion to be “a region in which the Radar Detector's sensitivity variesin proportion to the distance between it and the focal points thatdefine that region.” The beneficial result is that police radar canstill be reported, even if the police radar frequency matches one of thefrequencies that is locked for false alarm signals for a given region.This method is accordingly referred to as “Variable Sensitivity LockoutRegion” or VSLR.

In current GPS system without VSLR, the lockout decision is made byexamining the current location of the detector to determine if it fallswithin any nearby regions, which may be defined in an octagonal shapefor computational simplicity. The center of each of these Octagonalregions is referred to as a focal point. For each overlapping Octagonalregion, a comparison is made between the frequency of the detectedsignal and the frequency of signals determined as being locked in eachregion. If there is a match, current GPS systems will suppress thereporting of the signal.

In a VSLR-enhanced method 300, shown in FIG. 3, after a determination302 that the vehicle location is in the region of a locked signal, andit is determined 304 that the frequency of the detected signal is one ofthe frequencies locked in that region, extra steps must be performedbefore the signal suppression decision for each focal point can occur.

In a first step 306, the signal power level of the detected signal isdetermined, and in step 308, a threshold signal power level is computed,defined to be approximately 3 dB higher than the normal inversesquare-law signal propagation expected from the previously locked signalsource. If actual police radar at a locked frequency is being operatednear a locked signal source, the police radar should be reported (andnot suppressed) as soon as its signal level rises above this 3 dBthreshold. Accordingly, in step 310, the received signal level iscompared to the threshold, and if it is greater than the threshold, instep 312 an alert to the radar signal is produced, if the signal is notsubject to other filtering such as TSR or vehicle guidance systemsuppression as discussed above. However, if the signal is below thethreshold, then it is deemed to be from the locked stationary source,and (subject to optional processing discussed below) in step 316warnings of the signal are suppressed.

Since it is possible that police radar could be operated immediatelyadjacent to a rejected stationary source it is important that the VSLRmethod report of locked signals, even if they are weaker than the 3 dBthreshold. In current products of the assignee, a detected, lockedsignal is identified by a minimal visual indication on the radardetector display. This visual indication may, however, fail toadequately warn of a true police radar signal. Accordingly, In additionto using a signal level threshold as mentioned above, the VSLR methodmay optionally include a step 314 also use signal duration as a factorin the suppression decision. In one particular example, a time thresholdis computed by first computing an average value of the differencebetween the detected signal's power level and the threshold power level.Call this average difference X, measured in dB. If the signal iscontinuously detected, it will be reported (10*(1+X/4)) seconds afterthe first detection. Thus, a signal which remains roughly 4 dB below thethreshold will be reported after a 20 second delay.

Both the 3 dB signal level threshold of step 308 and the signal durationrequirement of step 314 will be applied to all focal points for alllocked false signals, which are the centers of nearby Octagonal regionsthat encompass the current position. Note, however, that if thesuppression criterion for any focal point results in a decision tosuppress an alert to a signal, none of the other focal points need to beconsidered relative to that signal. If all of the focal considerationsfail to conclude in a signal suppression decision, the signal will bereported.

Referring now to FIG. 4, methods of the present invention using camera42 (FIG. 1) can be explained. As part of its regular survey of radardata, social network data and GPS data, the processor in step 400 willactivate the camera and image processor to assess the scene visible tothe camera. In step 402 the image processor, or fusion processor itself,will search the image or video available from the camera for thepresence of a police vehicle or other vehicle of interest.

One circumstance of interest, step 404, is video reflecting a flashinglight bar on the road, typically indicative of police or other emergencyvehicles, according to a standardized color coding. Flashing policelights are strongly indicative of speed monitoring in the local area.

A second circumstance of interest, steps 406 and 408, is a vehicleprofile in the image of the road that matches a police car. Per step 406a vehicle with a profile that includes a light bar, that moves acrossthe field of vision in a manner suggesting a roadside traffic monitoringvehicle, is indicative of a possible speed trap. Alternatively, per step408, a vehicle with block colored panels that is similarly situated islikely a police vehicle and is suggestive of a speed trap.

In the event no circumstances of interest are identified, then the imageprocessing is done until re-initiated. However, if a circumstance ofinterest is identified in step 404, 406 or 408, then in step 412 theparticular circumstance is evaluated to determine if a user confirmationis required. Some circumstances, such as a flashing light bar, may beunambiguous as to their relevance to others in a social network, whereasother circumstances, such as a vehicle with block colored panels, may ormay not be of interest. Accordingly, user confirmation may be requiredfor some circumstances and not others. If user confirmation is requiredin step 412, then in step 416 the user is alerted to the possible policesighting and a confirmation is requested, which can be provided by abutton on the detector, or on a cord connected to the detector.

If a particular sighting is confirmed, or if no confirmation isrequired, then a police vehicle sighting and its GPS location and,optionally, details thereof such as the image or video, vehicledirection and/or speed, and are reported to the social network for usein alerting others. If a sighting is not confirmed, however, theprocessing finishes without alerting the social network.

The present invention has been described in connection with severalembodiments and some of those embodiments have been elaborated insubstantial detail. However, the scope of the invention is not to belimited by these embodiments which are presented as exemplary and notexclusive. The scope of the invention being claimed is set forth by thefollowing claims.

What is claimed is:
 1. A radar detector adapted to identify and suppressalerts of locally generated radar signals from vehicle guidance systems,the radar detector comprising: a radar receiver for detecting radarsignals; and signal processing electronics for controlling the radarreceiver and evaluating detected radar signals, the signal processingelectronics comprising a processor programmed via software to: perform alockout sequence during operation of the radar detector, the lockoutsequence comprising scanning a radar band for a vehicle guidance radarsignal that is consistently received and otherwise consistent withvehicle guidance systems signal emissions from the vehicle carrying theradar detector; identify a frequency of a vehicle guidance signalemission identified in the preceding step, and storing the frequency;and thereafter suppress warnings of radar signals at frequencies withina range including the stored frequency.
 2. The radar detector of claim 1wherein the lockout sequence is performed when power is first applied tothe radar detector.
 3. The radar detector of claim 1 wherein in thelockout sequence the signal processing electronics scan for radarsignals that are consistently received over time.
 4. The radar detectorof claim 1 wherein in the lockout sequence the signal processingelectronics scan for radar signals that are consistently received atmultiple locations.
 5. The radar detector of claim 1 wherein thefrequency is in one of K-band, Ka-band or X-band.
 6. The radar detectorof claim 1 wherein the signal processing electronics are configurable tobe placed in an operative mode in which the local source lockoutsequence is not performed.
 7. The radar detector of claim 1 wherein thesignal processing electronics perform a discrimination function toidentify that two discriminable signals appear near to the storedfrequency, the radar detector producing an alert in at least oneinstance when two discriminable signals are detected near to the storedfrequency.
 8. A radar detector implementing a method of identifyingvisual information relevant to speed monitoring, comprising: a. ahousing; b. a radar receiver for detecting radar signals integratedwithin the housing; c. electronics for controlling the radar receiverand evaluating detected radar signals integrated within the housing; andd. a camera integrated with the housing directed toward a road in thevicinity of a vehicle carrying the radar detector when the radardetector is in use, wherein the electronics gather image data from thecamera and process that data to identify visual information relevant tospeed monitoring in the image data.
 9. The radar detector of claim 8,wherein the electronics evaluate time-sequential images to identifyflashing lights characteristic of a functioning light bar on a police oremergency vehicle.
 10. The radar detector of claim 8, herein theelectronics evaluate one or more images to identify a vehicle profilecharacteristic of a police vehicle.
 11. The radar detector of claim 10wherein the vehicle profile includes a rooftop light bar.
 12. The radardetector of claim 10 wherein the vehicle profile includes highlycontrasting colored panels.
 13. The radar detector of claim 10 whereinthe vehicle profile comprises a vehicle stationed to monitor traffic.14. The radar detector of claim 8 wherein the electronics respond to oneor more images indicative of police activity by generating an alert toother drivers in a social network either unilaterally or uponconfirmation by a vehicle operator.